1. Field of the Invention
The present invention relates to apparatus for dispensing liquid from a container in successive quantums of equal quantity. In a broad sense, a quantum of a standard quantity of a given liquid can be considered to be a "dose" of that liquid, and therefore the apparatus of the invention may fairly be stated to be a dosing mechanism for successively dispensing liquid quantities of uniform volume.
2. Description of the Prior Art
In a known dosing mechanism of this type, shown in West German Patent 1,202,672, the two orifices connecting the dosing channels with the inner area of the liquid container are positioned in the side wall of the dosing mechanism. One orifice follows directly onto the partition closing the outer end of the dosing channel and the other orifice is at a corresponding axial spacing from the first orifice, so that the two orifices are on a straight line running parallel to the longitudinal axis of the dosing mechanism.
If the liquid container closed by the known dosing mechanism were turned upside down, liquid would flow out of the inner area of the container through the axially furthest outwardly located orifice in the dosing channel wall and into the said channel until the liquid level therein had risen to such an extent that it closed the second orifice, with the liquid container still turned upside down. In this condition, no further air could flow into the inner area of the liquid container and the liquid volume to be dispensed was reached.
However, even after the liquid had closed the second orifice, further liquid could flow from the inner area of the liquid container into the dosing channel, this being the so-called free liquid, this being the quantity of liquid which would flow out of the liquid container on opening the latter, but which would prevent air from entering the inner area of the container. The quantity of this free liquid is dependent inter alia on the specific gravity of the liquid, the height of the column of liquid and the quantity of air in the liquid container, which, due to the escape of the free liquid would then be under a partial vacuum. As a function of the liquid container filling level, the free liquid quantity would vary and could not flow out of the dosing channel, so that in actual fact only half the theoretically possible quantity of free liquid would enter the dosing channel and consequently the other half would be held back in the inner area of the liquid container.
The free liquid which escaped into the dosing channel over and beyond the desired volume in the known dosing mechanism lead to there being a partial vacuum in the inner area of the liquid container. If the liquid container were then tilted back into its normal position, due to the said vacuum in the liquid container during this process, the free liquid which had entered the dosing channel would be sucked back through the said orifice in the dosing channel wall into the inner area of the container, whereas the liquid volume defined by the spacing of the two orifices in the dosing channel wall would enter the collecting area between the end of the partition and the base of the dosing mechanism. By tilting the liquid container, the liquid could then be dispensed through the discharge channel, and, in the case of appropriate tilting, simultaneously a new volume of liquid of the desired size would enter the dosing channel.
The known dosing mechanism has the disadvantage of having a relatively high degree of imprecision in fixing the liquid volume to be dispensed, because the liquid level in the dosing channel can vary as a result of the fact that for filling the dosing channel, the user may bring the liquid container into different slope positions, the precise desired volume being obtained only if the liquid container is turned upside down in such a way that the longitudinal axis of the dosing channel is perpendicular. However, if this axis is varied from the perpendicular, the volume of the corresponding dose of liquid is either larger or smaller than desired, because although the liquid closes the two orifices in the dosing channel wall, the liquid level is inclined with respect to the longitudinal axis in accordance with the divergence of the longitudinal axis of the dosing channel from the perpendicular. In other words, the divergence of the liquid level from a plane perpendicular to the longitudinal axis of the dosing channel caused by the slope, leads to a difference between the actual liquid volume and that which should be dispensed.